Radiation-sensitive composition, pattern formation method, and radiation-sensitive acid generation agent

Abstract

The present invention provides a radiation-sensitive composition and a pattern formation method with which it is possible to form a resist film in which development defects can be minizied and sensitivity and CDU can be exhibited at a sufficient level when a next-generation technology is applied. The present invention also provides a radiation-sensitive acid generation agent that can be applied to the radiation-sensitive composition. The radiation-sensitive composition contains a polymer (A) containing structural units (I) having an acid dissociable group, and a solvent (C), the radiation-sensitive composition meeting criteria (i) and / or (ii) below. (i) Contains a radiation-sensitive acid generator (B) containing a first organic acid anion and a first onium cation, the first onium cation containing a halogen-free electron-withdrawing group that contains no halogen atoms, and the first organic acid anion being a sulfonic acid anion that contains an iodine atom. (ii) The polymer (A) is a radiation-sensitive acid-generating polymer (A1) containing structural units (IV) having a second organic acid anion and a second onium cation, the second onium cation containing a halogen-free electron-withdrawing group that contains no halogen atoms, and the second organic acid anion being a sulfonic acid anion that contains an iodine atom.

Description

Radiation-sensitive composition, pattern forming method, and radiation-sensitive acid generator

[0001] The present invention relates to a radiation-sensitive composition, a pattern forming method, and a radiation-sensitive acid generator.

[0002] Photolithography techniques using resist compositions are used to form fine circuits in semiconductor elements. A typical procedure involves, for example, exposing a coating of the resist composition to radiation through a mask pattern to generate an acid, which is then catalyzed by a reaction that causes a difference in the solubility of the resin in an alkaline or organic solvent-based developer between the exposed and unexposed areas, thereby forming a resist pattern on a substrate.

[0003] In the photolithography technology, pattern miniaturization is promoted by using short-wavelength radiation such as an ArF excimer laser or by combining this radiation with a liquid immersion lithography method. As a next-generation technology, the use of even shorter-wavelength radiation such as electron beams, X-rays, and EUV (extreme ultraviolet) is being attempted, and resist materials containing acid-generating compounds with structures that enhance the absorption efficiency of such radiation are also being investigated (Patent No. 4701231).

[0004] Patent No. 4701231

[0005] The above-mentioned next-generation technologies also require resist performance equal to or better than conventional ones in terms of sensitivity, critical dimension uniformity (CDU), which is an index of uniformity of line width and hole diameter, and development defects.

[0006] An object of the present invention is to provide a radiation-sensitive composition and a pattern forming method that are capable of forming a resist film that exhibits sufficient sensitivity and CDU and suppresses development defects when next-generation technologies are applied. Another object of the present invention is to provide a radiation-sensitive acid generator that can be used in the radiation-sensitive composition.

[0007] As a result of extensive research into solving the above problem, the present inventors have found that the above object can be achieved by employing the following configuration, and have thus completed the present invention.

[0008] In one embodiment, the present invention relates to a radiation-sensitive composition comprising: a polymer (A) containing a structural unit (I) having an acid-dissociable group; and a solvent (C), wherein the radiation-sensitive composition satisfies at least one of the following conditions (i) and (ii): (i) the radiation-sensitive composition comprises a radiation-sensitive acid generator (B) containing a first organic acid anion and a first onium cation, wherein the first onium cation is an onium cation containing a non-halogen-containing electron-withdrawing group that does not contain a halogen atom, and the first organic acid anion is a sulfonate anion containing an iodine atom; or (ii) the polymer (A) is a radiation-sensitive acid-generating polymer (A1) containing a structural unit (IV) having a second organic acid anion and a second onium cation, wherein the second onium cation is an onium cation containing a non-halogen-containing electron-withdrawing group that does not contain a halogen atom, and the second organic acid anion is a sulfonate anion containing an iodine atom.

[0009] This radiation-sensitive composition allows the construction of a resist film that satisfies the sensitivity and CDU requirements and suppresses the occurrence of development defects. While the reason for this is unclear, it is presumed as follows: The first onium cation of the radiation-sensitive acid generator (B) or the second onium cation of the radiation-sensitive acid-generating polymer (A1) contains an electron-withdrawing group, which allows it to react efficiently with electrons, thereby improving sensitivity and lithography performance. Furthermore, since the electron-withdrawing group contained in the onium cation does not contain a halogen atom, the onium cation is highly hydrophilic, increasing its affinity with alkaline developers and thereby suppressing the occurrence of development defects. Furthermore, the first organic acid anion of the radiation-sensitive acid generator (B) or the second organic acid anion of the radiation-sensitive acid-generating polymer (A1) is a sulfonate anion containing an iodine atom, which increases the electron yield and, as a result, enhances the sensitivity of the radiation-sensitive composition. Furthermore, when the first organic acid anion or the second organic acid anion contains an iodine atom, the molecular weight of the iodine atom can control acid diffusion, thereby improving CDU. It is presumed that the combined effects of these factors enable the resist performance and development defect suppression properties to be exhibited.

[0010] In another embodiment, the present invention relates to a pattern forming method, comprising the steps of: applying the radiation-sensitive composition directly or indirectly to a substrate to form a resist film; exposing the resist film; and developing the exposed resist film with a developer.

[0011] The pattern formation method uses the radiation-sensitive composition described above, which is capable of forming a resist film that has excellent sensitivity and CDU and is capable of suppressing the occurrence of development defects, and therefore can efficiently form a high-quality resist pattern.

[0012] In another embodiment, the present invention relates to a radiation-sensitive acid generator comprising: an onium cation containing an electron-withdrawing group containing no halogen atom; and a sulfonate anion containing an iodine atom.

[0013] By using a radiation-sensitive composition containing the radiation-sensitive acid generator, it is possible to form a resist film that has excellent sensitivity and CDU and in which the occurrence of development defects is suppressed.

[0014] Hereinafter, the embodiments of the present invention will be described in detail, but the present invention is not limited to these embodiments. Combinations of preferred embodiments are also preferred.

[0015] <Radiation-Sensitive Composition> The radiation-sensitive composition according to this embodiment (hereinafter also simply referred to as "composition") comprises a polymer (A) and a solvent (C) and satisfies at least one of the above (i) and (ii) (i.e., the radiation-sensitive composition comprises a radiation-sensitive acid generator (B) having a specific structure, or the polymer (A) is a radiation-sensitive acid-generating polymer (A1) containing a specific structural unit, or both). The composition may contain other optional components as long as the effects of the present invention are not impaired. When the radiation-sensitive composition comprises a radiation-sensitive acid generator (B) containing a specific structure, or the polymer (A) is a radiation-sensitive acid-generating polymer (A1) containing a specific structural unit, a resist film obtained from the radiation-sensitive composition can exhibit higher levels of sensitivity and CDU, and the occurrence of development defects can be suppressed.

[0016] <Polymer (A)> The polymer (A) is an aggregate of polymer chains containing a structural unit (I) having an acid-dissociable group (hereinafter, this aggregate will also be referred to as a "base polymer"). The polymers constituting the polymer (A) as a whole need only contain the structural unit (I). The polymer (A) may also contain a structural unit other than the structural unit (I). The polymer (A) may be a polymer having an acid-generating structure that generates acid upon exposure (radiation-sensitive acid-generating polymer (A1)), or may be a polymer not having an acid-generating structure.

[0017] The polymer having an acid-generating structure that generates acid upon exposure (radiation-sensitive acid-generating polymer (A1)) is an assembly of polymer chains containing a structural unit (I) having an acid-dissociable group and a structural unit (IV) having a second organic acid anion and a second onium cation (hereinafter, this polymer is also referred to as a "base polymer (A1)"), and is a component that generates acid upon exposure. The structural unit (I) and the structural unit (IV) may be contained in the same polymer chain, or the structural unit (I) may be contained in one polymer chain and the structural unit (IV) may be contained in another polymer chain. It is sufficient that the entire polymer constituting the radiation-sensitive acid-generating polymer (A1) contains the structural unit (I) and the structural unit (IV). The radiation-sensitive acid-generating polymer (A1) may contain structural units other than the structural unit (I) and the structural unit (IV).

[0018] In this specification, a form in which an onium salt structure is incorporated as part of a polymer is referred to as a "radiation-sensitive acid-generating polymer," and a form in which an onium salt structure exists alone as a compound (i.e., is isolated from a polymer) as a low-molecular-weight compound is referred to as a "radiation-sensitive acid generator."

[0019] The term "acid-dissociable group" refers to a group that substitutes a hydrogen atom in a carboxy group, a phenolic hydroxyl group, an alcoholic hydroxyl group, a sulfo group, or the like, and that dissociates under the action of an acid. The acid generated from the radiation-sensitive acid generator (B) or the radiation-sensitive acid-generating polymer (A1) upon exposure dissociates the acid-dissociable group in the structural unit (I) to generate a carboxy group or the like. This results in a difference in solubility in a developer between the exposed and unexposed areas of the resist film, making it possible to form a pattern.

[0020] From the viewpoints of sensitivity and CDU, the polymer (A) preferably contains an iodine atom, and more preferably contains an iodine-substituted aromatic ring structure.

[0021] (Structural Unit (I)) The structural unit (I) is a structural unit having an acid-dissociable group. The structural unit (I) is not particularly limited as long as it contains an acid-dissociable group, and examples thereof include a structural unit having a tertiary alkyl ester moiety, a structural unit having a structure in which the hydrogen atom of a phenolic hydroxyl group is substituted with a tertiary alkyl group, and a structural unit having an acetal bond. From the viewpoint of improving the pattern formability of the radiation-sensitive composition, a structural unit represented by the following formula (A1) (hereinafter also referred to as "structural unit (I-1)") is preferred.

[0022]

[0023] In the above formula (A1), R Ａ represents a hydrogen atom, a fluorine atom, an alkyl group having 1 to 10 carbon atoms, or a fluorinated alkyl group having 1 to 10 carbon atoms, and the alkyl group and the fluorinated alkyl group may have one or more linking groups -O-, -CO-, or a combination thereof between carbon atoms. Ａ１ is a hydrogen atom or a monovalent hydrocarbon group having 1 to 20 carbon atoms. Ａ２ and R Ａ３ are each independently a monovalent chain hydrocarbon group having 1 to 20 carbon atoms or a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, or a divalent alicyclic group having 3 to 20 carbon atoms formed by combining these groups together with the carbon atoms to which they are bonded. m1 and m2 are each independently 0 or 1. However, when m1 is 1, m2 is 1. When m1 is 0, L １ represents a single bond or a divalent linking group, and when m1 is 1, L １ represents a divalent linking group. In the above hydrocarbon group, chain hydrocarbon group, and alicyclic hydrocarbon group, some or all of the hydrogen atoms on the carbon atoms may be substituted with substituents such as halogen atoms.

[0024] L １Examples of the divalent linking group represented by the formula (I) include an alkanediyl group, a cycloalkanediyl group, an alkenediyl group, a cycloalkenediyl group, an arenediyl group, and groups having —CO—, —CS—, —O—, —S—, —SO— between the carbon-carbon bonds of these groups. ２ Examples of such groups include -, -NR'-, and groups containing a combination of two or more of these, or groups combining these. R' is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. Some or all of the hydrogen atoms in these groups may be substituted with a substituent such as a halogen atom such as a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom; a hydroxy group; a carboxy group; a cyano group; a nitro group; an alkyl group; an alkoxy group; an alkoxycarbonyl group; an alkoxycarbonyloxy group; an acyl group; an acyloxy group, or a group in which the hydrogen atoms of these groups are substituted with halogen atoms.

[0025] The alkanediyl group is preferably an alkanediyl group having 1 to 8 carbon atoms, such as a methanediyl group, an ethanediyl group, a 1,3-propanediyl group, or a 2,2-propanediyl group.

[0026] Examples of the cycloalkanediyl group include monocyclic cycloalkanediyl groups such as cyclopentanediyl and cyclohexanediyl groups, and polycyclic cycloalkanediyl groups such as norbornanediyl and adamantanediyl groups. The cycloalkanediyl group is preferably a cycloalkanediyl group having 5 to 12 carbon atoms.

[0027] Examples of the alkenediyl group include an ethenediyl group, a propenediyl group, a butenediyl group, etc. The alkenediyl group is preferably an alkenediyl group having 2 to 6 carbon atoms.

[0028] Examples of the arenediyl group include a benzenediyl group, a toluenediyl group, a naphthalenediyl group, etc. The arenediyl group is preferably an arenediyl group having 6 to 15 carbon atoms.

[0029] The above R Ａ１Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) include a chain hydrocarbon group having 1 to 20 carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, and a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms.

[0030] R Ａ１ ~R Ａ３ Examples of the monovalent linear hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) include a monovalent linear or branched saturated hydrocarbon group having 1 to 20 carbon atoms, or a monovalent linear or branched unsaturated hydrocarbon group having 2 to 20 carbon atoms. Examples of the monovalent linear or branched saturated hydrocarbon group having 1 to 20 carbon atoms include alkyl groups such as a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, a 2-methylpropyl group, a 1-methylpropyl group, a t-butyl group, an n-pentyl group, an isopentyl group, and a neopentyl group. Examples of the monovalent linear or branched unsaturated hydrocarbon group having 2 to 20 carbon atoms include alkenyl groups such as an ethenyl group, a propenyl group, and a butenyl group; and alkynyl groups such as an ethynyl group, a propynyl group, and a butynyl group.

[0031] The above R Ａ１ ~R Ａ３ Examples of the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the formula (I) include monocyclic or polycyclic saturated hydrocarbon groups, and monocyclic or polycyclic unsaturated hydrocarbon groups. Examples of monocyclic saturated hydrocarbon groups include cycloalkyl groups such as cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl. Examples of polycyclic saturated hydrocarbon groups include bridged alicyclic hydrocarbon groups such as norbornyl, adamantyl, tricyclodecyl, and tetracyclododecyl. Examples of monocyclic unsaturated hydrocarbon groups include monocyclic cycloalkenyl groups such as cyclopropenyl, cyclobutenyl, cyclopentenyl, and cyclohexenyl. Examples of polycyclic unsaturated hydrocarbon groups include polycyclic cycloalkenyl groups such as norbornenyl, tricyclodecenyl, and tetracyclododecenyl. The bridged alicyclic hydrocarbon group refers to a polycyclic alicyclic hydrocarbon group in which two carbon atoms that are not adjacent to each other among the carbon atoms that constitute the alicyclic ring are linked by a linking group containing one or more carbon atoms.

[0032] The above R Ａ１ Examples of the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms represented by the formula (I) include aryl groups such as a phenyl group, a tolyl group, a xylyl group, a naphthyl group, and an anthryl group; and aralkyl groups such as a benzyl group, a phenethyl group, and a naphthylmethyl group.

[0033] The above R Ａ１ is preferably a hydrogen atom, a linear or branched saturated hydrocarbon group having 1 to 20 carbon atoms, an alicyclic hydrocarbon group having 3 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms, and more preferably a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or a substituted or unsubstituted phenyl group.

[0034] R Ａ２ and R Ａ３ As the divalent alicyclic group having 3 to 20 carbon atoms constituted by combining these together with the carbon atoms to which they are bonded, a group in which one hydrogen atom has been removed from the above-mentioned monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms can be suitably used.

[0035] R Ａ２ and R Ａ３ are each independently a monovalent chain hydrocarbon group having 1 to 10 carbon atoms, or R Ａ２ and R Ａ３ are preferably a divalent alicyclic group having 3 to 20 carbon atoms formed by combining together with the carbon atoms to which they are bonded, and an alkyl group having 1 to 4 carbon atoms, or R Ａ２ and R Ａ３ are combined together with the carbon atoms to which they are attached to form a cycloalkanediyl group or a cycloalkenediyl group.

[0036] The above m1 is preferably 0, and L １ is preferably a single bond or an arenediyl group, and m2 is preferably 1.

[0037] Examples of the structural unit (I-1) include structural units represented by the following formulas (1-1) to (1-4).

[0038]

[0039] In the above formulas (1-1) to (1-4), R Ａ , R Ａ１ ~R Ａ３ has the same meaning as in formula (A1). i is an integer of 1 to 4. l is an integer of 0 to 2, and j is an integer of 0 to 9, satisfying 0≦j≦2l+5. k1 is an integer of 0 to 7, and k2 is an integer of 1 to 3.

[0040] In the above formulas (1-1) to (1-4), X represents L in the above formula (A1). １

[0049] The substituents shown in the following formula (1) can be suitably employed. Among these, a halogen atom or an alkyl group is preferred, and an iodine atom or a methyl group is more preferred. When j or k1 is 2 or more, the multiple Xs present may be the same or different.

[0041] R Ａ１ R is preferably a hydrogen atom, a methyl group, an ethyl group, an isopropyl group, or a t-butyl group. Ａ２ , R Ａ３ As the alkyl group, a methyl group, an ethyl group, and a t-butyl group are preferred.

[0042] Specific examples of the structural unit (I) include, but are not limited to, structures represented by the following formulae: Among the structures shown below, for the structures having an iodine-substituted aromatic ring structure, structures in which the iodine atom in the following formula is substituted with an atom or group other than an iodine atom, such as a hydrogen atom or other substituent, can also be suitably employed.

[0043] (In the formula, R Ａ has the same meaning as formula (A1) above.

[0044] (In the formula, R Ａ has the same meaning as formula (A1) above.

[0045] The base polymer may contain one type of structural unit (I) or a combination of two or more types.

[0046] The lower limit of the content of the structural unit (I) (the total content when multiple types are contained) relative to all structural units constituting the base polymer (or base polymer (A1)) is preferably 10 mol%, more preferably 20 mol%, even more preferably 30 mol%, and particularly preferably 35 mol%. The upper limit of this content is preferably 80 mol%, more preferably 70 mol%, and even more preferably 65 mol%. By ensuring that the content of the structural unit (I) falls within this range, the pattern formability of the radiation-sensitive composition can be further improved.

[0047] (Structural Unit (II)) The polymer (A) preferably further contains a structural unit (II) having a phenolic hydroxyl group. Examples of monomers that provide the structural unit (II) include, but are not limited to, those shown below. In the following formula, R Ａ is the same as above.

[0048]

[0049]

[0050] When the polymer (A) (or the radiation-sensitive acid-generating polymer (A1)) contains the structural unit (II), the lower limit of the content of the structural unit (II) (the total content when multiple structural units are contained) is preferably 15 mol %, more preferably 20 mol %, even more preferably 25 mol %, and particularly preferably 30 mol %, based on all structural units constituting the base polymer (or base polymer (A1)). The upper limit of the content is preferably 70 mol %, more preferably 60 mol %, even more preferably 55 mol %, and particularly preferably 50 mol %. By setting the content of the structural unit (II) within the above range, the pattern formability of the radiation-sensitive composition can be further improved.

[0051] (Structural Unit (III)) The polymer (A) may further contain another structural unit (III) containing a polar group such as an alcoholic hydroxyl group, a carboxyl group, a lactone ring, a sultone ring, an ether group, an ester group, a carbonyl group, or a cyano group. Monomers that provide the structural unit (III) include, but are not limited to, those shown below. In the following formula, R Ａ is the same as above.

[0052]

[0053]

[0054]

[0055]

[0056]

[0057]

[0058]

[0059]

[0060]

[0061]

[0062] When the polymer (A) (or the radiation-sensitive acid-generating polymer (A1)) contains the structural unit (III), the lower limit of the content of the structural unit (III) (the total content when multiple structural units are contained) is preferably 5 mol %, more preferably 8 mol %, and even more preferably 10 mol %, based on all structural units constituting the base polymer (or base polymer (A1)). The upper limit of the content is preferably 40 mol %, more preferably 30 mol %. By setting the content of the structural unit (III) within the above range, pattern adhesion can be further improved.

[0063] (Structural Unit (IV)) The polymer (A) may contain a structural unit (IV) having a second organic acid anion and a second onium cation. By incorporating the structural unit (IV) having an onium salt structure as a part of the polymer (A), the polymer (A) can be used as a "radiation-sensitive acid-generating polymer (A1)".

[0064] The form in which the organic acid anion and onium cation are contained in the structural unit (IV) of the base polymer is not particularly limited. The base polymer may have the organic acid anion as a side chain moiety, or may have the onium cation as a side chain moiety. "Having as a side chain moiety" means that the corresponding organic acid anion or onium cation is bonded (covalently bonded) to the main chain of the base polymer as a side chain structure. When the organic acid anion is bonded to the main chain of the base polymer as a side chain structure, the onium cation forms an ionic bond with the organic acid anion as a counter ion of the organic acid anion. On the other hand, when the onium cation is bonded to the main chain of the base polymer as a side chain structure, the organic acid anion forms an ionic bond with the onium cation as a counter ion of the onium cation. From the viewpoint of controlling the acid diffusion length, it is preferable that the base polymer have the organic acid anion as a side chain moiety.

[0065] The second organic acid anion is a sulfonate anion containing an iodine atom, and is preferably a sulfonate anion containing an iodine-substituted aromatic ring structure.

[0066] The second organic acid anion preferably has a sulfonate anion, and an electron-withdrawing group such as a fluorine atom or a fluorinated hydrocarbon group is bonded to a carbon atom adjacent to the sulfonate anion, thereby sufficiently increasing the strength of the acid generated by exposure to a level required for dissociation of the acid-dissociable group.

[0067] The structure of the second organic acid anion may be a sulfonate anion containing an iodine atom, and other structures are not particularly limited, but preferably include, for example, —O—, —CO—, a cyclic structure, or a combination thereof. Such combinations also include structures (heterocyclic structures) in which —O— or —CO— is incorporated into the cyclic structure as a ring-forming moiety.

[0068] The cyclic structure may be a monocycle, a polycycle, or a combination thereof. The cyclic structure may be an alicyclic structure, an aromatic ring structure, a heterocyclic structure, or a combination thereof. In the case of a combination, the ring structures may be bonded to each other in a chain structure, or two or more ring structures may form a fused ring structure or a bridged ring structure. A divalent heteroatom-containing group may be present between carbon atoms forming the backbone of the cyclic structure or chain structure, and some or all of the hydrogen atoms on the carbon atoms of the cyclic structure or chain structure may be substituted with other substituents. The second organic acid anion preferably has at least one cyclic structure selected from the group consisting of alicyclic structures and aromatic ring structures.

[0069] The alicyclic structure may be R Ａ２ and R Ａ３ A structure corresponding to the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms in the above formula can be suitably employed.

[0070] The aromatic ring structure is not particularly limited as long as it is a ring structure having aromaticity.Examples of the aromatic ring include aromatic hydrocarbon rings such as benzene ring, naphthalene ring, anthracene ring, phenalene ring, phenanthrene ring, pyrene ring, fluorene ring, perylene ring, and coronene ring, heteroaromatic rings such as furan ring, pyrrole ring, thiophene ring, phosphole ring, pyrazole ring, oxazole ring, isoxazole ring, thiazole ring, pyridine ring, pyrazine ring, pyrimidine ring, pyridazine ring, triazine ring, carbazole ring, and dibenzofuran ring, and combinations thereof.Among these, the aromatic ring is preferably a benzene ring.

[0071] Examples of the heterocyclic structure include: oxygen atom-containing alicyclic heterocyclic structures such as oxirane, tetrahydrofuran, tetrahydropyran, dioxolane, and dioxane; nitrogen atom-containing alicyclic heterocyclic structures such as aziridine, pyrrolidine, piperidine, and piperazine; sulfur atom-containing alicyclic heterocyclic structures such as thietane, thiolane, and thiane; alicyclic heterocyclic structures containing multiple types of heteroatoms such as morpholine, 1,2-oxathiolane, and 1,3-oxathiolane; oxygen atom-containing aromatic heterocyclic structures such as furan and benzofuran; nitrogen atom-containing aromatic heterocyclic structures such as pyrrole, pyrazole, and triazine; sulfur atom-containing aromatic heterocyclic structures such as thiophene; and aromatic heterocyclic structures containing multiple types of heteroatoms such as oxazole, isothiazole, and thiazine.

[0072] The heterocyclic structure includes a lactone structure, a cyclic carbonate structure, a sultone structure, a cyclic acetal structure, or a combination thereof.

[0073] The chain structure may be R Ａ２ and R Ａ３ A monovalent chain hydrocarbon group having 1 to 20 carbon atoms and represented by the following formula can be suitably used.

[0074] Examples of heteroatoms constituting the divalent heteroatom-containing group include oxygen atoms, nitrogen atoms, sulfur atoms, phosphorus atoms, silicon atoms, and halogen atoms. Examples of halogen atoms include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms.

[0075] Examples of the divalent heteroatom-containing group include -CO-, -C(=O)O-, -CS-, -NH-, -O-, -S-, -SO-, and -SO ２ -, or a combination thereof.

[0076] Examples of the substituents that substitute some or all of the hydrogen atoms on the carbon atoms of the cyclic structure or chain structure include L in the above formula (A1). １ The substituents in the following formula can be suitably employed.

[0077] The structural unit that provides the second organic acid anion is preferably a structural unit represented by the following formula (a1).

[0078]

[0079] In the formula, R Ａ is a hydrogen atom or a methyl group. １ is a single bond or an ester group. ２ is a linear, branched or cyclic alkylene group having 1 to 12 carbon atoms, a cycloalkylene group having 3 to 12 carbon atoms, or an arylene group having 6 to 10 carbon atoms, or a combination thereof, and some of the methylene groups constituting the alkylene group may be substituted with an ether group, an ester group or a lactone ring-containing group. ３ X is a single bond, an ether group, an ester group, a linear or branched alkylene group having 1 to 12 carbon atoms, or a cyclic cycloalkylene group having 3 to 12 carbon atoms, and some of the methylene groups constituting the alkylene group may be substituted with an ether group or an ester group. ２ and X ３ Some or all of the hydrogen atoms of the above X may be substituted with a heteroatom or a monovalent hydrocarbon group having 1 to 20 carbon atoms which may contain a heteroatom. ２ , X ３ At least one of the X's contains an iodine atom, ２ Preferably, the aromatic ring structure contains an iodine-substituted aromatic ring structure.

[0080] The above Rf １ ~Rf ４ are each independently a hydrogen atom, a fluorine atom, or a trifluoromethyl group, provided that at least one is a fluorine atom or a trifluoromethyl group.

[0081] X ２ and X ３The monovalent hydrocarbon group having 1 to 20 carbon atoms in the formula (I) is preferably an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or an aryl group having 6 to 20 carbon atoms, and some or all of the hydrogen atoms in these groups may be substituted with a heteroatom-containing group such as a hydroxy group, a carboxy group, a halogen atom, an oxo group, a cyano group, an amide group, a nitro group, a sultone group, a sulfone group, or a sulfonium salt-containing group, an alkoxy group, or an alkoxycarbonyl group, and some of the methylene groups constituting these groups may be substituted with an ether group, an ester group, a carbonyl group, a carbonate group, or a sulfonate ester group.

[0082] The structural units that provide the second organic acid anion are preferably represented by the following formulae (a1-1), (a2-1), and (a3-1), respectively.

[0083]

[0084] In the formula, R Ａ , Rf １ ~Rf ４ , X １ , and s1 have the same meaning as in formula (a1) above. ４８ is a linear, branched, or cyclic alkyl group having 1 to 4 carbon atoms, a halogen atom other than iodine, a hydroxy group, a linear, branched, or cyclic alkoxy group having 1 to 4 carbon atoms, or a linear, branched, or cyclic alkoxycarbonyl group having 2 to 5 carbon atoms. m is an integer of 1 to 4. n is an integer of 0 to 3, with the proviso that 0≦m+n≦4. s is an integer of 1 to 5.

[0085] Monomers that provide the above structural units include, but are not limited to, those shown below.

[0086]

[0087]

[0088]

[0089]

[0090]

[0091]

[0092]

[0093]

[0094]

[0095]

[0096]

[0097]

[0098]

[0099] (In the formula, R Ａ has the same meaning as the above formula (a1).

[0100] Examples of the second onium cation include the same as the first onium cation of the radiation-sensitive acid generator (B) described below.

[0101] Examples of the structural unit (IV) include those having the above-mentioned second onium cation as a counter ion to the anion of the structural unit that provides the above-mentioned second organic acid anion.

[0102] When the polymer (A) contains the structural unit (IV), the lower limit of the content of the structural unit (IV) (the total content when multiple types are contained) relative to all structural units constituting the base polymer (A1) is preferably 1 mol%, more preferably 3 mol%, and even more preferably 5 mol%. The upper limit of this content is preferably 30 mol%, more preferably 25 mol%, and even more preferably 20 mol%. By keeping the content of the structural unit (IV) within this range, the function as an acid generator can be fully exhibited.

[0103] (Method for synthesizing polymer (A)) The polymer (A) can be synthesized, for example, by adding a radical polymerization initiator to a monomer that provides the structural unit described above in an organic solvent and heating the mixture to polymerize it. Known polymerization initiators can be used for the polymerization.

[0104] When copolymerizing hydroxystyrene or hydroxyvinylnaphthalene, acetoxystyrene or acetoxyvinylnaphthalene may be used instead of hydroxystyrene or hydroxyvinylnaphthalene, and after polymerization, the acetoxy groups may be deprotected by the above-mentioned alkaline hydrolysis to form hydroxystyrene units or hydroxyvinylnaphthalene units. Alternatively, polymerization may be carried out without protecting the hydroxyl groups.

[0105] The polymer (A) has a polystyrene-equivalent weight average molecular weight (Mw) measured by gel permeation chromatography (GPC) using THF as a solvent of preferably 2,000, more preferably 4,000. The upper limit of Mw is preferably 30,000, more preferably 15,000. When Mw is within the above range, the resist material exhibits good pattern formability and heat resistance.

[0106] Furthermore, if the polymer (A) has a broad molecular weight distribution (Mw / Mn), the presence of low-molecular-weight and high-molecular-weight polymers may result in the appearance of foreign matter on the pattern after exposure, or the shape of the pattern may be deteriorated. As the pattern rule becomes finer, the effects of Mw and molecular weight distribution tend to become greater. Therefore, in order to obtain a resist material that is suitable for use with fine pattern dimensions, it is preferable that the molecular weight distribution of the polymer (A) is narrow, i.e., 1.0 to 2.0, and particularly 1.0 to 1.8.

[0107] The polymer (A) may contain two or more polymers having different composition ratios, Mws, and molecular weight distributions.

[0108] The lower limit of the content of the polymer (A) in the radiation-sensitive composition is preferably 40% by mass, more preferably 50% by mass, and even more preferably 60% by mass, based on the amount of the components other than the solvent (C) contained in the radiation-sensitive composition, and the upper limit of the content is preferably 99% by mass, more preferably 95% by mass.

[0109] <Radiation-sensitive acid generator (B)> The radiation-sensitive acid generator (B) contains a first organic acid anion and a first onium cation, the first onium cation being an onium cation containing a halogen-free electron-withdrawing group that does not contain a halogen atom, and the first organic acid anion being a sulfonate anion containing an iodine atom. The radiation-sensitive composition of the present invention contains at least one of the radiation-sensitive acid-generating polymer (A1) or the radiation-sensitive acid generator (B), and may contain both.

[0110] (First onium cation) The first onium cation contains a halogen-free electron-withdrawing group that does not contain a halogen atom. The halogen-free electron-withdrawing group may be any group that has electron-withdrawing properties and does not contain a halogen atom, for example, CN, COOR １１ , NO ２ , C.O.R. １２ , SOR １３ , and SO ２ R １４ (However, R １１ ~R １４ are preferably each independently at least one electron-withdrawing group selected from the group consisting of a hydrogen atom or a monovalent hydrocarbon group having 1 to 12 carbon atoms.

[0111] The first onium cation may contain a halogen-free electron-withdrawing group, or may contain a halogen-containing electron-withdrawing group in addition to the halogen-free electron-withdrawing group. Examples of such a halogen-containing electron-withdrawing group include a halogen atom such as a fluorine atom or an iodine atom, and a halogen-containing group.

[0112] The above R １１ ~R １４ The monovalent hydrocarbon group having 1 to 12 carbon atoms represented by the formula (A1) is Ａ１ Among the specific examples of monovalent hydrocarbon groups having 1 to 20 carbon atoms in R, those having 1 to 12 carbon atoms can be preferably used. １１ ~R １４ From the viewpoint of preventing development defects, the alkyl group is preferably an alkyl group having 1 to 6 carbon atoms or a group having a divalent heteroatom-containing group between the carbon atoms of this alkyl group.

[0113] Among the above non-halogen-containing electron-withdrawing groups, CN, COOR １１ (R １１ is an alkyl group having 1 to 6 carbon atoms), NO ２ , C.O.R. １２ (R １２ is an alkyl group having 1 to 6 carbon atoms), SO ２ R １４ (R １４ is preferably an alkyl group having 1 to 6 carbon atoms.

[0114] The number of the non-halogen-containing electron-withdrawing groups in the onium cation is preferably 1 to 5, and more preferably 1 to 4. Setting the number of non-halogen-containing electron-withdrawing groups within the above range is preferred from the viewpoint of hydrophilicity.

[0115] The first onium cation is preferably a sulfonium cation or an iodonium cation, and more specifically, is more preferably a cation represented by the following formula (1) or (2).

[0116] (In formula (1), Ar １ , Ar ２ and Ar ３ are each independently a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms. １ , Z ２ and Z ３ are each independently the above-mentioned non-halogen-containing electron-withdrawing group. １ , Z ２ and Z ３ If there are multiple Z １ , Z ２ and Z ３ are the same or different. １０１ , R １０２ and R １０３ are each independently a monovalent organic group (excluding non-halogen-containing electron-withdrawing groups), a halogen atom, a hydroxy group, or an amino group, or R １０１ , R １０２ and R １０３ Two of the R groups are linked together to form a ring structure. １０１ , R １０２and R １０３ If there are multiple R １０１ , R １０２ and R １０３ are the same or different. p1, p2, and p3 are each independently an integer of 0 to 3, provided that p1 + p2 + p3 is 1 or greater. q1, q2, and q3 are each independently an integer of 0 to 2, and p1 + q1, p2 + q2, and p3 + q3 are each 5 or less. (In formula (2), Ar ４ and Ar ５ are each independently a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms. ４ and Z ５ are each independently the above-mentioned non-halogen-containing electron-withdrawing group. ４ and Z ５ If there are multiple Z ４ and Z ５ are the same or different. １０４ and R １０５ R are each independently a monovalent organic group (excluding non-halogen-containing electron-withdrawing groups), a halogen atom, a hydroxy group, or an amino group. １０４ and R １０５ If there are multiple R １０４ and R １０５ are the same or different. p4 and p5 are each independently an integer of 0 to 3, provided that p4+p5 is 1 or greater. q4 and q5 are each independently an integer of 0 to 2, and p4+q4 and p5+q5 are each 5 or less.

[0117] Ar １ ~Ar ５ The monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms represented by R Ａ１ A monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms in the above formula can be suitably used.

[0118] Z １ ~Z ５ is the non-halogen-containing electron-withdrawing group, and Z １ ~Z ５ As for CN, COOR １１ (R１１ is an alkyl group having 1 to 6 carbon atoms), NO ２ , C.O.R. １２ (R １２ is an alkyl group having 1 to 6 carbon atoms), SO ２ R １４ (R １４ is preferably an alkyl group having 1 to 6 carbon atoms.

[0119] R １０１ ~R １０５ Examples of the monovalent organic group represented by the formula (A1) include a monovalent hydrocarbon group having 1 to 20 carbon atoms, a group having a divalent heteroatom-containing group between carbon atoms of the hydrocarbon group, a group in which some or all of the hydrogen atoms of the hydrocarbon group have been substituted with a monovalent substituent, or a combination thereof. １ The substituent in Ｙ４ R Ｙ５ (R Ｙ４ , R Ｙ５ are the same or different and each represents a hydrogen atom or a monovalent hydrocarbon group, or groups in which the hydrogen atom of these groups has been substituted with a halogen atom.

[0120] The above R １０１ ~R １０５ a monovalent hydrocarbon group having 1 to 20 carbon atoms in the above R Ｙ４ , R Ｙ５ The monovalent hydrocarbon group represented by the formula (A1) is Ａ１ A monovalent hydrocarbon group having 1 to 20 carbon atoms in the above formula can be suitably used.

[0121] As the heteroatom constituting the divalent heteroatom-containing group and the divalent heteroatom-containing group, those exemplified for the structural unit (IV) above can be suitably used.

[0122] Also, R １０１ , R １０２ and R １０３ Two of these may be linked to form a ring (i.e., a heterocycle containing a sulfur atom). １０１ , R １０２ and R １０３It is preferable that two of these groups are bonded to each other to form a single bond or a divalent linking group. Examples of the divalent linking group include -COO-, -OCO-, -CO-, -O-, -S-, -SO-, and -SO ２ R is an alkylene group, a cycloalkylene group, an alkenylene group, or a combination of two or more of these groups, and preferably has a total carbon number of 20 or less. １０１ , R １０２ and R １０３ When two of R are linked to each other to form a ring, １０１ , R １０２ and R １０３ Two of them may be bonded to each other to form -COO-, -OCO-, -CO-, -O-, -S-, -SO-, -SO ２ It is preferable to form -O-, -S- or a single bond. Among these, it is more preferable to form -O-, -S- or a single bond, and it is particularly preferable to form a single bond. １０１ may be bonded to each other to form a ring, and when q2 is 2 or more, a plurality of R １０２ may be bonded to each other to form a ring, and when q3 is 2 or more, a plurality of R １０３ may be linked to each other to form a ring. １０１ may be linked to each other to form a naphthalene ring together with the benzene ring to which they are bonded.

[0123] p1, p2, and p3 each independently represent an integer of 0 to 3, and p1+p2+p3 is 1 or greater, preferably 2 or greater. Furthermore, p1+p2+p3 is preferably 6 or less, more preferably 4 or less.

[0124] Specific examples of the sulfonium cation represented by the above formula (1) include the following: The fluorine atom or iodine atom in the onium cation shown below may be substituted with a hydrogen atom or other substituent, and the hydrogen atom on the aromatic ring may be substituted with an iodine atom, a fluorine atom, a group containing these atoms, or other substituent.

[0125] (In the formula, Me is a methyl group.)

[0126] (In the formula, Me is a methyl group and Et is an ethyl group.)

[0127] Specific examples of the iodonium cation include the following: In the onium cations shown below, the hydrogen atoms on the aromatic rings may be substituted with iodine atoms, fluorine atoms, groups containing these atoms, other substituents, etc.

[0128] (In the formula, Me is a methyl group.)

[0129] (First Organic Acid Anion) The first organic acid anion is a sulfonate anion containing an iodine atom, and is preferably represented by, for example, the following formula (A-1).

[0130]

[0131] In the above formula (A-1), R １Ｋ is a hydroxy group, a carboxy group, a fluorine atom, a chlorine atom, a bromine atom, or an amino group, or an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkoxycarbonyl group having 2 to 10 carbon atoms, an acyloxy group having 2 to 20 carbon atoms, or an alkylsulfonyloxy group having 1 to 20 carbon atoms, which may contain a fluorine atom, a chlorine atom, a bromine atom, a hydroxy group, an amino group, or an alkoxy group having 1 to 10 carbon atoms, or -NR ８Ｋ -C(=O)-R ９Ｋ Or -NR ８Ｋ -C(=O)-OR ９Ｋ and R ８Ｋ represents a hydrogen atom, or an alkyl group having 1 to 6 carbon atoms which may contain a halogen atom, a hydroxy group, an alkoxy group having 1 to 6 carbon atoms, an acyl group having 2 to 6 carbon atoms, or an acyloxy group having 2 to 6 carbon atoms; R ９Ｋis an alkyl group having 1 to 16 carbon atoms, an alkenyl group having 2 to 16 carbon atoms, or an aryl group having 6 to 12 carbon atoms, and may contain a halogen atom, a hydroxy group, an alkoxy group having 1 to 6 carbon atoms, an acyl group having 2 to 6 carbon atoms, or an acyloxy group having 2 to 6 carbon atoms. The alkyl group, alkoxy group, alkoxycarbonyl group, acyloxy group, acyl group, and alkenyl group may be linear, branched, or cyclic.

[0132] Of these, R １Ｋ Preferred examples of the alkyl group include a hydroxy group, a fluorine atom, a chlorine atom, a bromine atom, a methyl group, a methoxy group, and an ethoxy group, and more preferred examples are a hydroxy group and an ethoxy group.

[0133] In the above formula (A-1), rk is an integer of 0 to 2, qk is an integer of 1 to 5, and 1≦qk+rk≦5.

[0134] In the above formula (A-1), R ２Ｋ is a single bond, an ether bond, or an ester bond, or an alkylene group having 1 to 6 carbon atoms which may contain an ether bond or an ester bond. The alkylene group may be linear, branched, or cyclic.

[0135] In the above formula (A-1), L Ｋ is a divalent linking group. The divalent linking group is L in the above formula (A1). １ A divalent linking group represented by the formula (I) can be preferably used.

[0136] Rf １Ｋ , Rf ２Ｋ are each independently a hydrogen atom, a fluorine atom, or a trifluoromethyl group, and Rf １Ｋ and Rf ２Ｋ are preferably both fluorine atoms.

[0137] pk is an integer of 0 to 5.

[0138] Examples of the first organic acid anion represented by the above formula (A-1) include, but are not limited to, those shown below.

[0139]

[0140]

[0141]

[0142]

[0143]

[0144]

[0145]

[0146] The radiation-sensitive acid generator (B) includes any combination of the first organic acid anion and the first onium cation. Among these, the following are preferred.

[0147] (In the formula, Me represents a methyl group.)

[0148] (In the formula, Me represents a methyl group.)

[0149] (In the formula, Me represents a methyl group.)

[0150] The radiation-sensitive acid generator (B) can be synthesized by a known method, particularly a salt exchange reaction. A known radiation-sensitive acid generator other than the radiation-sensitive acid generator (B) can also be used in combination with the radiation-sensitive acid generator (B) as long as the effects of the present invention are not impaired.

[0151] These radiation-sensitive acid generators (B) may be used alone or in combination of two or more. The lower limit of the content of the radiation-sensitive acid generator (B) (total content when multiple types are used) is preferably 10 parts by mass, more preferably 20 parts by mass, and even more preferably 30 parts by mass, per 100 parts by mass of the polymer (A). The upper limit of the content is preferably 80 parts by mass, more preferably 75 parts by mass, and even more preferably 70 parts by mass, per 100 parts by mass of the polymer (A). This allows for excellent sensitivity and CDU to be exhibited during resist pattern formation.

[0152] When the polymer (A) is the radiation-sensitive acid-generating polymer (A1), the radiation-sensitive composition may contain a radiation-sensitive acid generator (B).

[0153] <Acid Diffusion Controller (D)> From the viewpoints of sensitivity and CDU, the radiation-sensitive composition preferably contains an acid diffusion controller (D). The acid diffusion controller (D) contains a third organic acid anion and a third onium cation, and generates an acid having a higher pKa than the acid generated from the radiation-sensitive acid generator (B) or the radiation-sensitive acid-generating polymer (A1) upon irradiation with radiation. The acid diffusion controller (D) containing a third organic acid anion and a third onium cation is preferably represented by the following formula (8-1) or (8-2):

[0154]

[0155] In the above formula (8-1) and formula (8-2), J ＋ is a sulfonium cation, and U ＋ is an iodonium cation. － and Q － are each independently R ８ SO ３ － , R ８ COO － , and (R ８ SO ２ ) N － Preferably, R is at least one selected from the group consisting of ８ COO － Further, examples of the compound include a compound represented by the formula (8-3) containing a sulfonium cation and an anion in the same molecule, and a compound represented by the formula (8-4) containing an iodonium cation and an anion in the same molecule. ８ is a monovalent organic group in the above formulas (8-1) and (8-2), and is a single bond or a divalent organic group in the above formulas (8-3) and (8-4).

[0156] From the viewpoint of sensitivity, the third organic acid anion is preferably an organic acid anion containing an iodine atom, and more preferably an organic acid anion containing an iodine-substituted aromatic ring structure.

[0157] Examples of the third organic acid anion include anions represented by the following formulas: Among the structures shown below, for the structures having an iodine-substituted aromatic ring structure, structures in which the iodine atom in the following formula is substituted with an atom or group other than an iodine atom, such as a hydrogen atom or other substituent, can also be suitably employed.

[0158]

[0159]

[0160]

[0161]

[0162]

[0163]

[0164]

[0165]

[0166] J ＋ Examples of the sulfonium cation include the onium cation represented by formula (1) or (2) of the radiation-sensitive acid generator (B) and a cation that does not contain a halogen-free electron-withdrawing group, which is obtained by removing the halogen-free electron-withdrawing group from the cation represented by formula (1) or (2). That is, a cation in formula (1) where p1, p2, and p3 are each independently an integer of 0 to 3 and p1 + p2 + p3 is 0 or greater, and a cation in formula (2) where p4 and p5 are each independently an integer of 0 to 3 and p4 + p5 is 0 or greater can be suitably used.

[0167] Moreover, as the third onium cation, from the viewpoint of suppressing development defects, an onium cation represented by the above formula (1) or (2) is preferred.

[0168] Specific examples of the tertiary onium cation include the following: The fluorine atom, iodine atom, and fluorine atom-containing group in the onium cations below may be substituted with a hydrogen atom or another substituent.

[0169] (In the formula, Me represents a methyl group.)

[0170]

[0171]

[0172]

[0173]

[0174]

[0175]

[0176] U ＋ Examples of the iodonium cation include diaryliodonium cations having one or more fluorine atoms.

[0177] The acid diffusion controller (D) can be synthesized by a known method, particularly a salt exchange reaction. Known acid diffusion controllers other than those mentioned above can also be used as long as they do not impair the effects of the present invention.

[0178] These acid diffusion controllers (D) may be used alone or in combination of two or more. The lower limit of the content of the acid diffusion controller (total when multiple types are used) relative to the radiation-sensitive acid generator (B) or the radiation-sensitive acid-generating polymer (A1) (relative to the total amount when both are included) is preferably 15 mol%, more preferably 20 mol%, and even more preferably 25 mol%. The upper limit of the content is preferably 100 mol%, more preferably 90 mol%, and even more preferably 80 mol%. This allows excellent sensitivity and CDU to be exhibited during resist pattern formation.

[0179] <Other Polymers> The radiation-sensitive composition of the present embodiment may contain, as another polymer, a polymer having a higher mass content of fluorine atoms than the base polymer (hereinafter also referred to as a "high-fluorine-content polymer"). When the radiation-sensitive composition contains a high-fluorine-content polymer, the high-fluorine-content polymer can be unevenly distributed in the surface layer of the resist film relative to the base polymer, and as a result, the state of the resist film surface and the component distribution in the resist film can be controlled to desired states.

[0180] The high-fluorine content polymer preferably has a structural unit represented by the following formula (6) (hereinafter also referred to as "structural unit (V)"): In addition, for example, the high-fluorine content polymer may have at least one of the structural units (I) to (III) in the base polymer, if necessary.

[0181] In the above formula (6), R ７３ is a hydrogen atom, a methyl group, or a trifluoromethyl group. Ｌ represents a single bond, an oxygen atom, a sulfur atom, -COO-, or -SO ２ ONH-, -CONH- or -OCONH-. ７４ is a monovalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms or a monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms.

[0182] The above R ７３ As the alkyl group, from the viewpoint of copolymerizability of the monomer that gives the structural unit (V), a hydrogen atom or a methyl group is preferred, and a methyl group is more preferred.

[0183] Above G Ｌ As the group, from the viewpoint of copolymerizability of the monomer that gives the structural unit (V), a single bond and —COO— are preferred, and —COO— is more preferred.

[0184] The above R ７４ Examples of the monovalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) include a linear or branched alkyl group having 1 to 20 carbon atoms in which some or all of the hydrogen atoms have been substituted with fluorine atoms.

[0185] The above R ７４ Examples of the monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the formula (I) include a monocyclic or polycyclic hydrocarbon group having 3 to 20 carbon atoms in which some or all of the hydrogen atoms have been substituted with fluorine atoms.

[0186] The above R ７４As the alkyl group, a fluorinated chain hydrocarbon group is preferable, a fluorinated alkyl group is more preferable, and a 2,2,2-trifluoroethyl group, a 1,1,1,3,3,3-hexafluoropropyl group, a 5,5,5-trifluoro-1,1-diethylpentyl group, and a 1,1,1,2,2,3,3-heptafluoro-6-methylheptan-4-yl group are even more preferable.

[0187] When the high-fluorine-content polymer has the structural unit (V), the lower limit of the content of the structural unit (V) is preferably 50 mol%, more preferably 60 mol%, and even more preferably 70 mol%, based on all structural units constituting the high-fluorine-content polymer. The upper limit of the content is preferably 100 mol%, more preferably 95 mol%, and even more preferably 90 mol%. By setting the content of the structural unit (V) within the above range, the mass content of fluorine atoms in the high-fluorine-content polymer can be more appropriately adjusted, thereby further promoting uneven distribution of fluorine atoms in the surface layer of the resist film.

[0188] The lower limit of Mw of the high fluorine content polymer is preferably 1,000, more preferably 2,000, even more preferably 3,000, and particularly preferably 5,000. The upper limit of Mw is preferably 50,000, more preferably 30,000, even more preferably 20,000, and particularly preferably 15,000.

[0189] The Mw / Mn of the high fluorine content polymer is usually at least 1, and more preferably at least 1.1. The Mw / Mn is usually at most 5, preferably at most 3, more preferably at most 2.5, and even more preferably at most 2.2.

[0190] The lower limit of the content of the high-fluorine-containing polymer is preferably 0.5 parts by mass, more preferably 1 part by mass, and even more preferably 2 parts by mass, relative to 100 parts by mass of the polymer (A). The upper limit of the content is preferably 10 parts by mass, more preferably 8 parts by mass, and even more preferably 5 parts by mass. By setting the content of the high-fluorine-containing polymer within the above range, the high-fluorine-containing polymer can be more effectively localized to the surface layer of the resist film, thereby suppressing elution from the upper part of the pattern during development and improving the rectangularity of the pattern. The radiation-sensitive composition may contain one or more high-fluorine-containing polymers.

[0191] (Method for synthesizing high fluorine content polymer) The high fluorine content polymer can be synthesized by the same method as the above-mentioned method for synthesizing the base polymer.

[0192] <Solvent (C)> The radiation-sensitive composition according to this embodiment contains a solvent (C). The solvent (C) is not particularly limited as long as it is a solvent that can dissolve or disperse the polymer (A) and optional additives and the like.

[0193] Examples of the solvent (C) include alcohol-based solvents, ether-based solvents, ketone-based solvents, amide-based solvents, ester-based solvents, and hydrocarbon-based solvents.

[0194] Examples of alcohol-based solvents include monoalcohol-based solvents having 1 to 18 carbon atoms, such as iso-propanol, 4-methyl-2-pentanol, 3-methoxybutanol, n-hexanol, 2-ethylhexanol, furfuryl alcohol, cyclohexanol, 3,3,5-trimethylcyclohexanol, diacetone alcohol, and methyl 2-hydroxyisobutyrate; polyhydric alcohol-based solvents having 2 to 18 carbon atoms, such as ethylene glycol, 1,2-propylene glycol, 2-methyl-2,4-pentanediol, 2,5-hexanediol, diethylene glycol, dipropylene glycol, triethylene glycol, and tripropylene glycol; and polyhydric alcohol partially etherified solvents in which some of the hydroxy groups in the above-mentioned polyhydric alcohol-based solvents have been etherified.

[0195] In the present embodiment, alcoholic acid ester solvents such as methyl lactate, ethyl lactate, propyl lactate, butyl lactate, methyl 2-hydroxyisobutyrate, i-propyl 2-hydroxyisobutyrate, i-butyl 2-hydroxyisobutyrate, and n-butyl 2-hydroxyisobutyrate are also included in the alcoholic solvents.

[0196] Examples of ether-based solvents include dialkyl ether-based solvents such as diethyl ether, dipropyl ether, and dibutyl ether; cyclic ether-based solvents such as tetrahydrofuran and tetrahydropyran; aromatic ring-containing ether-based solvents such as diphenyl ether and anisole (methyl phenyl ether); and polyhydric alcohol ether-based solvents obtained by etherifying the hydroxy groups of the above-mentioned polyhydric alcohol-based solvents.

[0197] Examples of the ketone solvent include chain ketone solvents such as acetone, butanone, and methyl-iso-butyl ketone; cyclic ketone solvents such as cyclopentanone, cyclohexanone, and methylcyclohexanone; and 2,4-pentanedione, acetonylacetone, and acetophenone.

[0198] Examples of the amide solvent include cyclic amide solvents such as N,N'-dimethylimidazolidinone and N-methylpyrrolidone; and chain amide solvents such as N-methylformamide, N,N-dimethylformamide, N,N-diethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, and N-methylpropionamide.

[0199] Examples of ester-based solvents include monocarboxylic acid ester-based solvents such as n-butyl acetate; polyhydric alcohol partial ether acetate-based solvents such as diethylene glycol mono-n-butyl ether acetate, propylene glycol monomethyl ether acetate, and dipropylene glycol monomethyl ether acetate; lactone-based solvents such as γ-butyrolactone and valerolactone; carbonate-based solvents such as diethyl carbonate, ethylene carbonate, and propylene carbonate; and polyvalent carboxylic acid diester-based solvents such as propylene glycol diacetate, methoxytriglycol acetate, diethyl oxalate, ethyl acetoacetate, and diethyl phthalate.

[0200] Examples of hydrocarbon solvents include aliphatic hydrocarbon solvents such as n-hexane, cyclohexane, and methylcyclohexane; and aromatic hydrocarbon solvents such as benzene, toluene, di-isopropylbenzene, and n-amylnaphthalene.

[0201] Among these, ester-based solvents, ketone-based solvents, alcohol-based solvents, and ether-based solvents are preferred, polyhydric alcohol partial ether acetate-based solvents, cyclic ketone-based solvents, lactone-based solvents, alcohol acid ester-based solvents, polyhydric alcohol partial ether-based solvents, and monocarboxylic acid ester-based solvents are more preferred, and propylene glycol monomethyl ether acetate, cyclohexanone, γ-butyrolactone, propylene glycol monomethyl ether, diacetone alcohol, ethyl lactate, and methyl 2-hydroxy-2-methylpropionate are even more preferred. The radiation-sensitive composition may contain one or more solvents.

[0202] <Other Optional Components> The radiation-sensitive composition may contain other optional components in addition to the components described above. Examples of the other optional components include a crosslinking agent, a localization promoter, a surfactant, an alicyclic skeleton-containing compound, and a sensitizer. These other optional components may be used alone or in combination of two or more.

[0203] <Method for Preparing Radiation-Sensitive Composition> The radiation-sensitive composition can be prepared, for example, by mixing the polymer (A), the solvent (C), and, if necessary, other optional components in a predetermined ratio. After mixing, the radiation-sensitive composition is preferably filtered, for example, through a filter having a pore size of about 0.05 μm to 0.4 μm. The solids concentration of the radiation-sensitive composition is usually 0.1% by mass to 50% by mass, preferably 0.5% by mass to 30% by mass, and more preferably 1% by mass to 20% by mass.

[0204] <<Pattern Forming Method>> The pattern forming method of the present embodiment includes: a step (1) of applying the radiation-sensitive composition directly or indirectly to a substrate to form a resist film (hereinafter also referred to as a "resist film forming step"); a step (2) of exposing the resist film to light (hereinafter also referred to as an "exposure step"); and a step (3) of developing the exposed resist film with a developer (hereinafter also referred to as a "development step").

[0205] According to the pattern forming method, since the radiation-sensitive composition capable of forming a resist film excellent in sensitivity, CDU, and suppression of development defects is used, a high-quality resist pattern can be formed.

[0206] [Resist Film Forming Step] In this step (step (1) above), a resist film is formed from the radiation-sensitive composition. Examples of substrates on which the resist film is formed include conventionally known substrates such as silicon wafers, silicon dioxide wafers, and aluminum-coated wafers. Alternatively, an organic or inorganic anti-reflective coating, such as those disclosed in JP-B-6-12452 and JP-A-59-93448, may be formed on the substrate. Examples of coating methods include spin coating, casting coating, and roll coating. After coating, pre-baking (PB) may be performed, if necessary, to volatilize the solvent in the coating film. The PB temperature is typically 60°C to 160°C, preferably 80°C to 140°C. The PB time is typically 5 seconds to 600 seconds, preferably 10 seconds to 300 seconds. The thickness of the resist film formed is preferably 10 nm to 1,000 nm, more preferably 10 nm to 500 nm.

[0207] When the subsequent exposure step is carried out using radiation with a wavelength of 50 nm or less, it is preferable to use a polymer having the structural unit (II) as the base polymer in the composition.

[0208] [Exposure Step] In this step (the above step (2)), the resist film formed in the above step (1), the resist film formation step, is exposed by irradiating it with radiation through a photomask (or, in some cases, through an immersion medium such as water). Examples of radiation used for exposure include electromagnetic waves such as visible light, ultraviolet light, far ultraviolet light, EUV (extreme ultraviolet), X-rays, and gamma rays; and charged particle beams such as electron beams and alpha rays, depending on the line width of the desired pattern. Among these, far ultraviolet light, electron beams, and EUV are preferred, with ArF excimer laser light (wavelength 193 nm), KrF excimer laser light (wavelength 248 nm), electron beams, and EUV being more preferred, and electron beams and EUV with wavelengths of 50 nm or less, which are positioned as next-generation exposure technologies, being even more preferred.

[0209] After the exposure, post-exposure baking (PEB) is preferably performed to promote dissociation of acid-dissociable groups in the polymer or the like in the exposed portions of the resist film by the acid generated from the radiation-sensitive acid generator upon exposure. This PEB results in a difference in solubility in a developer between the exposed and unexposed portions. The PEB temperature is typically 50°C to 180°C, preferably 80°C to 150°C. The PEB time is typically 5 seconds to 600 seconds, preferably 10 seconds to 300 seconds.

[0210] [Development Step] In this step (step (3) above), the resist film exposed in the exposure step (step (2) above) is developed with a developer. This allows a predetermined resist pattern to be formed. After development, the resist film is generally washed with a rinse liquid such as water or alcohol, and then dried.

[0211] In the case of alkaline development, examples of the developer used in the development include an alkaline aqueous solution containing at least one alkaline compound dissolved therein, such as sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate, aqueous ammonia, ethylamine, n-propylamine, diethylamine, di-n-propylamine, triethylamine, methyldiethylamine, ethyldimethylamine, triethanolamine, tetramethylammonium hydroxide (TMAH), pyrrole, piperidine, choline, 1,8-diazabicyclo-[5.4.0]-7-undecene, and 1,5-diazabicyclo-[4.3.0]-5-nonene. Among these, an aqueous TMAH solution is preferred, and a 2.38% by mass aqueous TMAH solution is more preferred.

[0212] In the case of organic solvent development, examples of the organic solvent include hydrocarbon solvents, ether solvents, ester solvents, ketone solvents, and alcohol solvents, as well as solvents containing an organic solvent. Examples of the organic solvent include one or more of the solvents listed above as solvents for the radiation-sensitive composition. Among these, ester solvents and ketone solvents are preferred. As the ester solvent, acetate ester solvents are preferred, with n-butyl acetate and amyl acetate being more preferred. As the ketone solvent, chain ketones are preferred, with 2-heptanone being more preferred. The content of the organic solvent in the developer is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 99% by mass or more. Examples of components other than the organic solvent in the developer include water and silicone oil.

[0213] Examples of the developing method include a method of immersing a substrate in a tank filled with a developer for a certain period of time (dip method), a method of piling up a developer on the surface of the substrate by surface tension and leaving it to stand for a certain period of time to develop (puddle method), a method of spraying the developer onto the surface of the substrate (spray method), and a method of continuously discharging the developer while scanning a developer discharging nozzle at a constant speed onto a substrate that is rotating at a constant speed (dynamic dispense method).

[0214] <Radiation-Sensitive Acid Generator> The radiation-sensitive acid generator of the present embodiment contains an onium cation containing an electron-withdrawing group containing no halogen atom, and a sulfonate anion containing an iodine atom.

[0215] Examples of the radiation-sensitive acid generator include the same compounds as the radiation-sensitive acid generator (B).

[0216] The present invention will be specifically explained below with reference to Synthesis Examples, Examples and Comparative Examples, but the present invention is not limited to the following Examples. Measurement methods for various physical properties are shown below.

[0217] [Mw and Mn] The Mw and Mn of the polymer were measured by gel permeation chromatography (GPC) using GPC columns (two "G2000HXL", one "G3000HXL", and one "G4000HXL" columns) manufactured by Tosoh Corporation under the following conditions: Eluent: tetrahydrofuran (manufactured by Wako Pure Chemical Industries, Ltd.) Flow rate: 1.0 mL / min Sample concentration: 1.0 mass% Sample injection amount: 100 μL Column temperature: 40° C. Detector: differential refractometer Standard material: monodisperse polystyrene

[0218] <Synthesis of Polymer (A)> Base polymers (A-1) to (A-15) were synthesized as polymer (A) according to the following method. Compounds represented by the following formulas (M-1) to (M-16) (hereinafter also referred to as "monomers (M-1) to (M-16)") were used to synthesize polymer (A). In the following synthesis examples, unless otherwise specified, "parts by mass" means a value when the total mass of the monomers used is taken as 100 parts by mass, and "mol %" means a value when the total number of moles of the monomers used is taken as 100 mol %.

[0219] [Synthesis Examples A-1 to A-15] Synthesis of Polymers (A-1) to (A-15) Each monomer was combined and copolymerized in tetrahydrofuran (THF) solvent, followed by isolation and drying to obtain base polymers (A-1) to (A-15) with the compositions shown below. The Mw and dispersity (Mw / Mn) of the resulting base polymers were confirmed by the above-mentioned GPC (solvent: THF, standard: polystyrene). The amount of each structural unit used, as well as the Mw and Mw / Mn values, are also shown in Table 1. For example, in Synthesis Example A-6, "M-2 / M-1=25 / 25" means that M-2 and M-1 are contained in a molar ratio of 25:25, and their total is 50 mol %. Therefore, the composition of base polymer (A-6) is M-2 / M-1 / M-6=25 / 25 / 50 (molar ratio). In the table, "-" indicates that the corresponding component was not used.

[0220]

[0221]

[0222] Synthesis Example B-1 Synthesis of Compound (B-1) Compound (B-1) was synthesized according to the following reaction scheme.

[0223] Compound (PPPB-1) (16 mmol) and benzene (80 mmol) were placed in a container containing dichloromethane (30 mL) and cooled on ice. Trifluoromethanesulfonic anhydride (18 mmol) was added dropwise and the mixture was stirred at room temperature. After cooling on ice, 100 mL of ultrapure water was added dropwise. After washing with water, the mixture was concentrated to dryness and recrystallized to obtain compound (PPB-1).

[0224] Compound (PPB-1) (10 mmol) was allowed to react with QAE Sephadex (registered trademark) manufactured by Sigma-Aldrich in the presence of methanol, and the solvent was distilled off to obtain compound (PB-1).

[0225] Compound (PB-1) (10 mmol) and compound (P-1) (10 mmol) were added to a container containing dichloromethane (50 mL) and ultrapure water (50 mL). After stirring at room temperature, the mixture was washed with water and then concentrated to dryness to obtain compound (B-1).

[0226]

[0227] [Synthesis Examples B-2 to B-14] Synthesis of Compounds (B-2) to (B-17) By appropriately selecting precursors and selecting the same recipe as in Synthesis Example B-1, compounds represented by the following formulas (B-2) to (B-17) were synthesized.

[0228] <Preparation of Radiation-Sensitive Composition> The polymer (A), radiation-sensitive acid generator (B), acid diffusion controller (D), and solvent (C) used in preparing the radiation-sensitive composition are shown below. In the following examples and comparative examples, unless otherwise specified, "parts by mass" means a value when the mass of the polymer (A) used is taken as 100 parts by mass, and "mol %" means a value when the number of moles of the radiation-sensitive acid generator (B) or radiation-sensitive polymer (A-10) or (A-11) used is taken as 100 mol %.

[0229] [Polymer (A)] As the polymer (A), the base polymers (A-1) to (A-15) synthesized in the above Synthesis Examples A-1 to A-15 were used.

[0230] [Radiation-Sensitive Acid Generator (B)] As the radiation-sensitive acid generator (B), the compounds (B-1) to (B-17) synthesized in the above Synthesis Examples B-1 to B-17 were used.

[0231] [Acid Diffusion Controller (D)] As the acid diffusion controller (D), compounds represented by the following formulae (D-1) to (D-6) were used.

[0232] [Solvent (C)] The following solvents were used as solvent (C): (C-1): propylene glycol monomethyl ether acetate (C-2): propylene glycol monomethyl ether (C-3): diacetone alcohol

[0233] Example 1 Preparation of Radiation-Sensitive Composition (R-1) 100 parts by mass of (A-1) as the base polymer (A), 60 parts by mass of (B-1) as the radiation-sensitive acid generator (B), 70 mol % of (D-1) as the acid diffusion controller (D) relative to (B-1), 5,500 parts by mass of (C-1) as the solvent (C), and 1,500 parts by mass of (C-2) were mixed. The resulting mixture was filtered through a filter with a pore size of 0.2 μm to prepare a radiation-sensitive composition (R-1).

[0234] [Examples 2 to 35 and Comparative Examples 1 to 3] Preparation of radiation-sensitive compositions (R-2) to (R-35) and (CR-1) to (CR-3) Radiation-sensitive compositions (R-2) to (R-35) and (CR-1) to (CR-3) were prepared in the same manner as in Example 1, except that the types and amounts of each component shown in Table 2 below were used.

[0235]

[0236] <Evaluation> The radiation-sensitive compositions prepared above were evaluated for sensitivity, CDU, and number of development defects according to the following methods. The evaluation results are shown in Table 3 below.

[0237] [Sensitivity] A composition for forming a bottom antireflective coating (Brewer Science's ARC66) was applied to a 12-inch silicon wafer using a spin coater (Tokyo Electron Limited's CLEAN TRACK ACT12), and then heated at 205°C for 60 seconds to form a bottom antireflective coating with an average thickness of 105 nm. Each radiation-sensitive composition shown in Table 2 was applied to this bottom antireflective coating using the spin coater, and post-baked (PB) at 130°C for 60 seconds. This was then cooled at 23°C for 30 seconds to form a resist film with an average thickness of 45 nm. This resist film was exposed to light using an EUV scanner (ASML's NXE3300 (NA 0.33, σ 0.9 / 0.6, quadruple-pole illumination, 50 nm pitch on wafer, +20% bias hole pattern mask)). PEB was performed on a hot plate at 100°C for 60 seconds, and development was performed in a 2.38 mass% aqueous solution of tetramethylammonium hydroxide (TMAH) for 30 seconds to form a resist pattern with 25 nm holes and a 50 nm pitch (hereinafter also referred to as a "25 nm contact hole pattern"). The exposure dose for forming the 25 nm contact hole pattern was determined as the optimum exposure dose, and this optimum exposure dose was used for sensitivity (mJ / cm ２ The smaller the sensitivity, the better. The sensitivity was 60 mJ / cm ２ If it is less than 60 mJ / cm, it is rated as "A" (very good). ２ More than 63mJ / cm ２ The following cases are rated as "B" (good) and 63 mJ / cm ２ If the value exceeded this, it was evaluated as "C" (poor).

[0238] [CDU] A 25 nm contact hole pattern was formed in the same manner as above, using the optimal exposure dose determined in the [Sensitivity] section above. The formed resist pattern was observed from above using a scanning electron microscope (Hitachi High-Tech Corporation's "CG-5000"), and a total of 800 hole diameters were measured at random points. The dimensional variation (3σ) was determined and this was taken as CDU (unit: nm). The smaller the CDU value, the smaller the variation in hole diameter over a long period, indicating better results. CDU was evaluated as "A" (very good) for values ​​less than 3.3 nm, "B" (good) for values ​​3.3 nm or greater but less than 3.6 nm, and "C" (poor) for values ​​3.6 nm or greater.

[0239] [Number of Development Defects] A resist film was exposed to an optimum exposure dose and developed to form a 25 nm contact hole pattern. The number of defects on the wafer was measured using a defect inspection system (KLA-Tencor's "KLA2810"). Of the defects measured, defects with a diameter of 0.5 μm or less were determined to be originating from the resist film. The number of development defects was determined as "A" (very good) if the number of defects determined to be originating from the resist film was less than 30, "B" (good) if the number was 30 to 50, and "C" (poor) if the number was more than 50.

[0240] The resist patterns formed through the above-described EUV exposure were evaluated, and as a result, the radiation-sensitive compositions of the examples had good sensitivity and CDU, and also had a small number of development defects.

[0241] The radiation-sensitive composition and the method for forming a resist pattern described above enable the formation of a resist pattern that has good sensitivity to exposure light, an excellent CDU, and few development defects, and therefore can be suitably used in the processing of semiconductor devices, which are expected to become even more miniaturized in the future.

Claims

1. A polymer (A) containing a structural unit (I) having an acid-dissociable group, Solvent (C) and Includes, A radiation-sensitive composition that satisfies at least one of the following conditions (i) or (ii). (i) A radiation-sensitive acid generator (B) comprising a first organic acid anion and a first onium cation, wherein the first onium cation is an onium cation containing a halogen-free electron-withdrawing group that does not contain a halogen atom, and the first organic acid anion is a sulfonic acid anion containing an iodine atom. (ii) The polymer (A) is a radiation-sensitive acid-generating polymer (A1) further comprising a structural unit (IV) having a second organic acid anion and a second onium cation, wherein the second onium cation is an onium cation containing a halogen-free electron-withdrawing group that does not contain a halogen atom, and the second organic acid anion is a sulfonic acid anion containing an iodine atom.

2. The above halogen-free electron-withdrawing group is CN, COOR １１ NO ２ COR １２ , SOR １３ , and SO ２ R １４ (However, R １１ ~R １４ The radiation-sensitive composition according to claim 1, wherein each of the is an electron-withdrawing group selected independently from the group consisting of a hydrogen atom or a monovalent hydrocarbon group having 1 to 12 carbon atoms.

3. The radiation-sensitive composition according to Claim 1, wherein the halogen-free electron-withdrawing group is at least one electron-withdrawing group selected from the group consisting of CN, COOR 11, NO 2, COR 12, SOR 13, and SO 2 R 14 (wherein R 11 to R 13 are each independently a hydrogen atom or a monovalent hydrocarbon group having 1 to 12 carbon atoms, and R 14 is a chain-like hydrocarbon group having 1 to 12 carbon atoms).

4. The radiation-sensitive composition according to Claim 1, wherein the halogen-free electron-withdrawing group is at least one electron-withdrawing group selected from the group consisting of CN, COOR 11 (R 11 is an alkyl group having 1 to 6 carbon atoms), NO 2, COR 12 (R 12 is an alkyl group having 1 to 6 carbon atoms), and SO 2 R 14 (R 14 is an alkyl group having 1 to 6 carbon atoms).

5. The radiation-sensitive composition according to claim 1, wherein the number of halogen-free electron-withdrawing groups in the first onium cation or the second onium cation is 1 to 5.

6. The radiation-sensitive composition according to claim 1, wherein the first onium cation or the second onium cation is a sulfonium cation or an iodonium cation.

7. The radiation-sensitive composition according to claim 1, further comprising an acid diffusion control agent (D) which comprises a third organic acid anion and a third onium cation, and which generates an acid having a higher pKa than the acid generated from the above-mentioned radiation-sensitive acid generator (B) or radiation-sensitive acid-generating polymer (A1) upon irradiation with radiation.

8. The radiation-sensitive composition according to claim 7, wherein the third onium cation is an onium cation containing the halogen-free electron-withdrawing group.

9. The above onium cation is represented by the following formula (1) or the following formula (2), in the radiation-sensitive composition according to any one of claims 1 to 8. 【Chemistry 1】 (In formula (1), Ar １ 、 Ar ２ and Ar ３ are each independently a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms. Z １ Z ２ and Z ３ Each of these is independently a halogen-free electron-withdrawing group. Z １ Z ２ and Z ３ If multiple Zs exist, １ Z ２ and Z ３ They are either identical or different from one another. R １０１ , R １０２ and R １０３ Each of these is independently either a monovalent organic group (excluding halogen-free electron-withdrawing groups), a halogen atom, a hydroxyl group, or an amino group, or R １０１ , R １０２ and R １０３ Two of them are linked together to form a ring structure. １０１ , R １０２ and R １０３ If multiple R １０１ , R １０２ and R １０３ They are either identical or different from one another. p1, p2, and p3 are each independent integers between 0 and 3, provided that p1 + p2 + p3 is greater than or equal to 1. q1, q2, and q3 are each independent integers between 0 and 2. p1 + q1, p2 + q2, and p3 + q3 are all less than or equal to 5. 【Chemistry 2】 (In formula (2), Ar ４ and Ar ５ Each of these is independently a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms. Z ４ and Z ５ Each of these is independently a halogen-free electron-withdrawing group. Z ４ and Z ５ If multiple Zs exist, ４ and Z ５ They are either identical or different from one another. R １０４ and R １０５ Each of these is independently a monovalent organic group (excluding halogen-free electron-withdrawing groups), a halogen atom, a hydroxyl group, or an amino group. １０４ and R １０５ If multiple R １０４ and R １０５ They are either identical or different from one another. p4 and p5 are independent integers between 0 and 3, provided that p4 + p5 is greater than or equal to 1. q4 and q5 are each independent integers between 0 and 2. p4 + q4 and p5 + q5 are both less than or equal to 5.

10. The radiation-sensitive composition according to claim 7, wherein the third organic acid anion has at least one selected from the group consisting of sulfonic acid anions, carboxylic acid anions, and sulfonimide anions.

11. The radiation-sensitive composition according to claim 1, wherein the first organic acid anion or the second organic acid anion contains an iodine-substituted aromatic ring structure.

12. The radiation-sensitive composition according to claim 1, wherein the polymer (A) comprises a structural unit (II) having a phenolic hydroxyl group.

13. The above polymer (A) is a radiation-sensitive composition according to claim 1, comprising an iodine atom.

14. A step of forming a resist film by directly or indirectly applying the radiation-sensitive composition according to any one of claims 1 to 8 to a substrate, The process of exposing the above-mentioned resist film, The process involves developing the exposed resist film with a developer solution. A pattern formation method including the following.

15. The pattern forming method according to claim 14, wherein the above exposure is performed using extreme ultraviolet light or an electron beam.

16. An onium cation containing an electron-withdrawing group that does not contain a halogen atom, Sulfonate anions containing an iodine atom and A radiation-sensitive acid generator containing [unclear].

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